Observation Date: 01/03/2021
Lost Trail BC
Mostly overcast and skies today with moderate- strong SW winds. Snow fell most of the day and accumulated ~3in new.
New Snow: 3-6″
Dug several pits on a NE aspect @`~8000′ on a 30* slope to identify and observe fracture character in weak layers associated with our persistent slab problem. Our average snow depth was 160cm. The two most reactive layers we found were ~35cm and ~130cm from the surface. We performed numerous Compression Tests and observed sudden fractures at both of these layers. We performed a Rutschblock test and recorded a score of 4 with most of the soft slab block releasing ~35cm down on a layer of 4-8mm buried surface hoar (SH) (see photo). This was our primary layer of concern because it was easily triggered by a skier and the slab will only get more pronounced with increased load and/or settlement.
The 130cm down layer is concerning because it’s deep and could be triggered from an area of shallower snow or by a significant loading event.
There were 4 distinct layers of surface hoar recorded:
Down 32cm (4-8mm), 37cm (4mm), 86cm (6-8mm over rounding facets 1mm) and 93 cm (8-10mm over rounding facets 2mm).
The lower weak layer down 132cm (depth hoar 2-8mm over facets 2mm) (see photo) failed at the top of the Nov-Dec faceted snow layer (widespread weak basal layer).
Observer: George D’Angelo